Where particles move from an area of high concentration to an area of low concentration- e.g gases can diffuse through one another like a smell spreading through a room

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What do dissolved particles diffuse in and out of cells through?

Cell membranes

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Diffusion and osmosis both involve stuff moving from what?

An area where there's a high concentration of it, to an area where there's a lower concentration of it

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Why is it that active transport comes in?

This is because some substances need to move in the other direction

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What do the gases and dissolved substances have to move through?

Some sort of exchange surface

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What do exchange surfaces have to allow?

Enough of the necessary substances to pass through

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Why are exchange surfaces adapted to maximise effectiveness?

-They are thin so substances only have a short distance to diffuse -They have a large surface area so lots of a substance can diffuse at once -Exchange surface in animals have lots of blood vessels to get stuff out of the blood quickly

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Exchanging substances gets more difficult in what?

Bigger and more complex organisms

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What does the structure of leaves do?

Let gases diffuse in and out of cells

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What diffuses into the hair spaces within the leaf?

Carbon dioxide- which it then diffuses into the cells where photosynthesis happens

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The underneath of the leaf is a what?

An exchange surface

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What is the exchange surface covered in?

Biddy little holes called stomata which the carbon dioxide diffuses in through

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What also does oxygen and water vapor diffuse through?

The stomata- water vapor is lost from all over the leaf surface but most of it is lost through the stomata

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What is the stomata controlled by?

Guard cells

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What do guard cells do?

Close the stomata when the plant is losing water fast than it is being replaced by the roots- plants would wilt without guard cells

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What does the flattened shape of the leaf increase?

The area of this exchange surface so it's more effective

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What happens when the walls of the cells inside the leaf form another exchange surface?

The air spaces inside the leaf increase the area of this surface so there's more chance of carbon dioxide to get into the cells

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After the water vapor evaporates from the cells inside the leaf what happens?

It escapes by diffusion as there's a lot of it inside the leaf and less of it in the air outside